Pre-stressed rolling mills



Nov. 22, 1966 J. A. TRACY 3,286,501

PRE-STRESSED ROLLING MILLS Filed July 30, 1963 5 Sheets-Sheet 1 l NVENTOR JOHN ANDRE TRACY BY g ATTORNEYS Nov. 22, 1966 J. A. TRACY 3,286,501

I PRE-STRESSED ROLLING MILLS Filed July 30, 1963 3 Sheets-Sheet z Jig;

INVENTOR JOHN ANDRE TRACY AT TOR N EYS Nov. 22, 1966 J. A. TRACY PRE-STRESSED ROLLING MILLS 5 Sheets-Sheet 5 Filed July 30, 1963 IN VENTOR JOHN ANDRE TRACX h fl/m/lwwwd 9 M ATTORNEYS United States Patent Ofifice The present invention relates to pre-stressed rolling mills, and isparticularly applicable to frameless mills of the type in which the bearing chocks at each side are interconnected by pre-stressed columns, each assembly of .chocks and columns forming, ineffect, part ofthe mill frame.

In the conventional-construction of mills of this type,

the columns are held in a stressed condition by bearing nuts screwed on the-ends of-thecolumns and bearing against the top of'the upper chocks and the bottom of the lower chocks. Therollgap for the reception of material to berolled is adjusted by the insertion of shims or other spacing means between the upper and lowerchocks. The setting of these mills to obtain a roll gap of predetermined size is, however, a difficult and tedious operation, since the shims suffer deformation when subjected to the pre-stressing force and the ,pre-stressing force must be released before shims can be inserted or withdrawn from between the chocks.

It has been proposed toprovide a pre-stressed frameless mill with adjustable screw jacks positioned between the upper and lower chocks, and with bearing nuts screwed on the ends of the columns, the pitch of the screw threads on the jacks being equal to the pitch of the screw threads on the bearing nut. The screw nuts are, however, subjected to the full pre-stressing force and thefrictional-resistance to rotation of the nuts, while underthe full prestressing force,is too great to permit adjustment of both the screw nuts and the jacks during rolling.

Furthermore, in known constructions of mills of this type, the assembly of chocks and columns forms a very rigid structure. The chocks and bearings must consequently be machined and mounted together with a high degree of accuracy in order to prevent any misalignment of the roll necks in the bearings, and'the pre-stressing forcemust be removed before any relative adjustment betweenthe chocks can beelfected.

One of the objects of the invention is to provide an improved construction of a pre-stressed frameless mill in which the roll gap maybe adjusted during rolling when the columns are in a stressed condition.

Another object of the invention is to provide an improved construction of a pre-stressed rolling mill which facilitates erection of the mill and reducesthe possibility of misalignment of the bearings, even when the rolls are subjected to an-exceptionally large separating force.

Accordingto the invention, there is provided a frameless mill of the type refereredto, wherein the upper and lower chocks are spaced apart by adjustable jacks, and the columns are maintained in a stressed condition by-hydraulic means, the jacks being adjustable to vary-thespacing between the chocks, and hence the roll-gap between the rolls during rolling.

The-hydraulic meansmay consist of piston andicylinder units, of which the pistons are mounted ionthe columns, and the cylinders'are slidable'relative to the columns, and held against the chocks by hydraulic pressure. During rollingthe pre-stressing forceis opposed by the separating force acting on the rolls due to the deformation of the material, so that the screw jacks are subjected to only the difference between the pre-stressing and separating 3,286,501 Patented Nov. 22, 1966 forces. The loading on the screw jacks is thus sufficiently small to enable the chocks to-be adjusted during an actual rolling operation.

The-loading oneach, jack, and consequently the axial deformation of each jack, is preferably maintained constant during rolling-despite variation in the-separating .force due to variations in the thickness, width or temperature of the'material-being rolled. Thisis preferably obtained'by the control systemdescribed and claimed in my co-pending British application No. 27,276/ 61, now Patent No. 955,l64,'in which the loading on each jack is continuously measured, and the-prestressing force regulated in accordance with theloading on the jack so-as to maintain the difference between thepre-stressing andseparating forces substantially constant.

According to another aspectof the invention,the two chocks at each side of a pre-stressed rolling mill are provided with sets of pads positioned between the two chocks .and between the chocks and thepre-stressing means, the .pads of each set contacting each other on matchingtconvex and concave surfaces respectively which are so arranged. on the padsthat each choc-k'is free to tilt or rock relative to the other chock about an axis perpendicular to both the axis of the associated roll and the common plane through the axes of the rolls.

According-t0 a further feature of thisinvention, intermediary pads may be provided between two parts having convex (or concave) bearing surfaces, the co-acting surfaces of the intermediary pad being of matching concave or convex shape.

In the case of a frameless mill, the assembly of chocks and columns at each side of the mill is preferably supported on two trunnions or pivot shafts arranged on opposite sides of the assembly and extending perpendicular to'both the axis of one of the rolls and the common plane through the axes of the rolls.

The freedom of the chocks to tilt relativeto one another has considerable advantages in the erection and operation of the mill. During erection, the chocks can be tilted to correct misalignment of the roll necks in the bearings, and during'operation of the mill thechocks are free to follow deflections of the roll necks should the rolls be subjected to an exceptionally large separating force,

thereby preventing damage to the bearings due to misalignto be construed as covering eithera single chock in the case of a two-high mill orboth the associated back-up roll chock and the working roll chock in the case of a four-high mill.

A preferred construction of apre-st-ressed frameless rolling mill according to the invention will now be described by way of example with reference to the accompanying drawings, of which:

FIG. 1 is a'front elevation of a rolling mill according to the inventiompartly in section,

FIG. 2 is a section of the mill of'FIG. 1 along the line 2-2 of FIG. 1,

FIG. 3 shows a detail of this mill on an enlarged scale,

FIGS. 4 and 5 are exploded views of two different varieties of pads.

The mill comprises two working rolls 11, 12 arranged in superposed relationship, two back-up rolls 14, 15 arranged one above and one below the working rolls and two chock assemblies 17, 18supportingthe working and back-up rolls.

Each chock assembly comprises upper and lower backup chocks 20, 21 interconnected by two hydraulically prestressed columns 23 extending through aligned vertical bores in the back-up chocks 20, 21, two power-operated screwjacks 25 positioned between the back-up chocks, and upper and lower working roll chocks 27, 28 which have a close sliding fit between the side walls of recesses 30 formed in the lower and upper ends of the upper and lower back-up chocks 20, 21 respectively. The sides of the lower back-up chocks are provided with upwardly projecting lugs 32 which form guides for the upper backup chock 20 and facilitate erection of the mill.

The working rolls 11, 12 are rotatably mounted in bearings 37, 38 in the working roll chocks 27, 28 respectively, and the back-up rolls 14, 15 are rotatably mounted in bearings 34, 35 in the back-up chocks 20, 21 respectively. Either the working rolls or the back-up rolls may be driven in any conventional and well-known manner. Each chock assembly 17, 18 is supported by trunnions 40 secured to the sides of the lower back-up chocks 21 and mounted on pedestals 42 which rest on a foundation of the mill. The trunnions 40 are so arranged that their axes extend perpendicular to both the axis of the lower back-up roll 15 and the common plane through the axes of all the rolls.

The upper end of each column 23 projects above the upper back-up chock 20 and is provided with a screw nut 44, and the lower end of each column projects below the lower back-up chock 21 and extends through an opening in the base of a cylinder 46 of a single-acting hydraulic unit 48. The piston 50 of the hydraulic unit is secured in the lower end of the column 23, and the cylinder 46 is axially movable relative to the piston and column. Sealing rings 52 on the piston and in the wall of the opening in the base of the cylinder 46 prevent leakage of liquid supplied to the cylinder.

Each screw nut 44 bears against a set of two superposed annular bearing pads 54, 55 which surround the column 23 and are located in a recess 57 in the upper end of the upper back-up chock 20, and the cylinder 46 of the hydraulic unit 48, when supplied with liquid under pressure, bears against a similar set of two annular bearing pads 59, 60 which surround the column 23 and are located in a recess 62 in the lower end of the lower back-up chock 21. The outer pad 54 or 60 of each set, i.e., the pad adjacent the associated screw nut 44 or cylinder 46 fits closely around the column 23, but is spaced from the wall of the recess 57, 62 respectively, and the inner pad 55, 59 of each set fits closely against the wall of the recess 57, 62, but is spaced from the wall of the column 23. The adjoining faces of the two pads in each set have matching part-spherical surfaces, the radial centre R or R of which is located at the point of intersection of the column axis and the horizontal plane through the axis of the associated back-up roll 14 or 15.

Each screw-jack 25 comprises outer and inner sleeves 64, 65 surrounding the portion of the column 23 between the back-up chocks 20, 21, the inner sleeve 65 being screwed on a thread on the inner wall of the outer sleeve 64 and projecting above the outer sleeve. The inner sleeve 65 has a loose sliding fit on splines 70 on the column 23, and the outer sleeve 64 is mounted in a circular recess 69 in the upper end of the lower back-up chock 21. The outer sleeve 64 is rotatable within the circular recess 69 by a power-driven worm 71 in mesh with teeth 72 formed on the outer wall of the outer sleeve 64, the worm being rotatably mounted in a bore 73 in the lower back-up chock 21. Since the inner sleeve 65 of the screw jack 25 is restrained against rotation by the splines 70 on the column 23, rotation of the outer sleeve 64 by means of the worm 71 will move the inner sleeve 65 along the splines on the column and thereby adjust the overall length of the jack 25.

An annular loadmeter 75 is located in a recess 76 in the lower end of the upper back-up chock 20, and an intermediate pad 78 is interposed between the upper end of the inner sleeve 65 and that load meter (FIG. 3). The adjoining faces of the inner sleeve 65, the pad 78 and the loadmeter 75 are formed with matching partspherical surfaces, the radial centres of which coincide with the radial centre R R of the part-spherical surfaces of the set of pads 54, 55 and 59, 60 on the upper and lower ends of the column 23.

The working roll chocks 27, 28 are urged apart by hydraulic piston-and-cylinder units 80, in known manner, in order to maintain each working roll 11, 12 in contact with its associated back-up roll 14, 15. The working rolls co-operate to form a roll gap for the reception of material M to be rolled, the height of the roll gap being determined by the spacing between the back-up rolls 14, 15, which in turn is determined by the overall length of the screw-jacks 25.

The assembly of chocks and column at each side of the mill is pre-stressed by supply of liquid under pressure to the cylinders 46 of the hydraulic units 48. The pressure of liquid in the hydraulic units forces the cylinders upwards against the sets of bearing pads 59, 60 on the lower back-up chock 21 and forces the nuts 44 on the upper ends of the columns downwards against the sets of bearing pads 54, 55 on the upper back-up chock 20. The upper and lower back-up chocks 20, 21 are thus forced against the upper and lower end faces of the loadmeters 75 and screw-jacks 25 respectively.

The trunnion mounting 40 on the lower back-up chocks 21 and the part-spherical surfaces on the sets of bearing pads 54, 55 and 59, 60, and on the adjoining faces of the loadmeters 75, intermediary pads 78 and screw-jacks 25 permit a small degree of tilting or rocking movement of each back-up chock about an axis perpendicular to that of the associated back-up roll and to the common plane through the axes of the rolls, the columns 22 being provided with sufficient clearance in their bores in the back-up chocks 20, 21 to permit rocking movement of the chocks.

This freedom of tilting or rocking movement of the back-up chocks 20, 21 is particularly advantageous during a rolling operation if the rolls are subjected to an excessively large separating force which would exert a correspondingly large bending moment on the rolls and cause a correspondingly large deflection of the back-up rolls 14, 15, including their necks 82, 83. In such circumstances, the chocks can follow the movements of the roll necks to maintain the bearings 34, 35 in the back-up chocks 20, 21 in alignment with the roll necks 82, 83. Damage to the bearings due to misalignment under heavy load is thus avoided.

The erection, dismantling and maintenance of the improved mill is particularly simple, due to the fact that the columns 23 and hydraulic units 48 are readily removable, and alignment of the roll necks in the bearings 34, 35 is facilitated by the ability of the chocks 20, 21 to tilt relative to one another.

Erection of the mill is in addition facilitated by the sets of bearing pads 54, 55 and 59, 60 between the chocks 20, 21 and both the screw nuts 44 and the hydraulic cylinders 46, respectively. Upon rocking movement of the back-up chocks 20, 21, the inner pads 55, 59 follow the movements of the back-up chocks 20, 21, since these pads fit closely in their locating recesses 57, 62 in the chocks, and the outer pads 54, 60 remain square to the screw nuts 44 and cylinders 46 respectively, since these parts in turn fit closely on the columns 23. The bearing pads thus obviate the necessity, existing in known mills, for machining or otherwise modifying the pre-stressing means on the ends of the clumns to ensure a square fit on the chocks.

On a rolling operation, the pre-stressing force exerted on the back-up chocks 20, 21 by the hydraulic units 48 is maintained at a value in excess of the separating force acting on the rolls. The screw jacks 25 are however only subjected to a load corresponding to the difference between the pre-stressing and separating forces. The load ing .on the jacks is thus comparatively small, so that the jacks can be adjusted to vary the roll gap while a rolling operation is in progress.

The loadmeters 75 are magneto-elastic elements which provide a voltage output proportional to the loading on the element. Each loadmeter is subjected to the same loading as its associated screw-jack 25, and the output of the loa'dmeter thus gives an indication of the loading on the screw-jack.

The output of each l-oadmeter 75 is, however, preferably arranged so to regulate the pressure of liquid in the associated hydraulic unit 48 that the loading on each loadmeter and screw-jack remains at a predetermined value. The :axial deformation of the jack 25, due to its loading, then remains constant and the roll gap between the working rolls 10, 11 similarly remains constant. Such a control of the pre-stressing force exerted by each hydraulic unit 48 is particularly advantageous in circumstances in which the proportion of the separating force taken by the chocks at one end of the mill differs from the proportion of the separating force taken by the chocks at the other end of the mill, for example in a case in which the material being rolled is offset from the centre line of the mill.

The matching surfaces on the pads may be spherical, as shown in FIG. 4, or they may be cylindrical, as shown in FIG. 5. In the latter case, the axes of the cylindrical surfaces coincide with the axis which is perpendicular to both the axes of the associated roll and the common plane through the roll.

The invention is capable of other embodiments than the one described. For example, the upper back-up chocks 20 may be mounted on the trunnions 40, the rolls may be arranged in a vertical position, or other changes may be made.

I claim:

1. A frameless rolling mill in which the bearing chocks at each side of the mill form together one assembly, and in which each assembly is interconnected by pre-stressed columns, sets of bearing pads being positioned between the two chocks of one assembly as well as between one chock of one of said assemblies and the prestressing means, the pads of each set contacting each other on matching convex and concave bearing surfaces respectively which are so arranged on the pads that a chock of an assembly is free to tilt or rock relative to the other chock of the same assembly and about an axis perpendicular to both the axis of the associated roll and the common plane through the axes of the rolls.

2. A frameless rolling mill according to claim 1, in which one end of each column projects beyond one bearing chock of an assembly and is provided With a screw nut, the screw nut bearing against a set of two super-posed annular bearing pads which surround the column and are located in a recess in the end of said chock, and in which the opposite end of each column projects beyond the other chock of the same assembly and extends through an opening in the base of a cylinder of a single-acting hydraulic pre-stressing unit, the cylinder, when supplied with liquid under pressure, bearing against a set of two super-posed annular bearing pads which surround the column and are located in a recess in the end of said other chock.

3. A frameless rolling mill according to claim 1, in which the assembly of chocks and columns at each side of the mill is supported on two trunnions or pivot shafts arranged on opposite sides of the assembly and extending perpendicular to both the axis of one of the rolls and the common plane through the axes of the rolls.

4. A frameless rolling mill according to claim 1, in which an intermediary pad is provided between the two chocks of one assembly, said intermediary pad having bearing surfaces of convex or concave shape which are in contact with matching surfaces provided on the two chocks or on parts arranged between the chocks and the intermediary pad.

5. A frameless rolling mill according to claim 4, in which an intermediary pad is interposed between a loadmeter bearing against one chock and an adjustable jack bearing against the other chock of the same assembly.

6. A frameless rolling mill according to claims 1 and 4, in which the centres of curvature of the convex or concave bearing surfaces of the intermediary pads coincide with the centres of curvature of the bearing surfaces of the pads on the ends of a column.

References Cited by the Examiner UNITED STATES PATENTS 2,355,677 8/ 1944 Ransome 291.5 2,625,843 1/1953 Arp 29l.5 2,635,324 4/1953 Berthiez 29--1.5 3,124,982 3/1964 Neumann 72240 X CHARLES W. LANHAM, Primary Examiner.

C. H. HITTSON, G. P. CROSBY, Assistant Examiners. 

1. A "FRAMELESS" ROLLING MILL IN WHICH THE BEARING CHOCKS AT EACH SIDE OF THE MILL FORM TOGETHER ONE ASSEMBLY, AND IN WHICH EACH ASSEMBLY IS INTERCONNECTED BY PRE-STRESSED COLUMNS, SETS OF BEARING PADS BEING POSITIONED BETWEEN THE TWO CHOCKS OF ONE ASSEMBLY AS WELL AS BETWEEN ONE CHOCK OF ONE OF SAID ASSEMBLIES AND THE PRESTRESSING MEANS, THE PADS OF EACH SET CONTACTING EACH OTHER ON MATCHING CONVEX AND CONCAVE BEARING SURFACES RESPECTIVELY WHICH ARE SO ARRANGED ON THE PADS THAT A CHOCK OF AN ASSEMBLY IS FREE TO TILT OR ROCK RELATIVE TO 